Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions

Abstract

Shifts in the timing and magnitude of the spring plankton bloom in response to climate change have been observed across a wide range of aquatic systems. We used meta-analysis to investigate phenological responses of marine and freshwater plankton communities in mesocosms subjected to experimental manipulations of temperature and light intensity. Systems differed with respect to the dominant mesozooplankton (copepods in seawater and daphnids in freshwater). Higher water temperatures advanced the bloom timing of most functional plankton groups in both marine and freshwater systems. In contrast to timing, responses of bloom magnitudes were more variable among taxa and systems and were influenced by light intensity and trophic interactions. Increased light levels increased the magnitude of the spring peaks of most phytoplankton taxa and of total phytoplankton biomass. Intensified size-selective grazing of copepods in warming scenarios affected phytoplankton size structure and lowered intermediate (20-200 lm)-sized phytoplankton in marine systems. In contrast, plankton peak magnitudes in freshwater systems were unaffected by temperature, but decreased at lower light intensities, suggesting that filter feeding daphnids are sensitive to changes in algal carrying capacity as mediated by light supply. Our analysis confirms the general shift toward earlier blooms at increased temperature in both marine and freshwater systems and supports predictions that effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.

The response of temperate aquatic ecosystems to global warming: novel insights from a multidisciplinary project

“…This prediction was supported by the mesocosm experiments by Müren et al (2005) and O'Connor et al (2009). Within AQUASHIFT, the Baltic Sea mesocosm experiments (Klauschies et al 2012;Sommer et al 2012;Winder et al 2012), the microcosm experiments of Burgmer and Hillebrand (2011), and modeling Lake Constance phytoplankton (Tirok and Gaedke 2007b) also showed a declining phytoplankton biomass, while the lake mesocosms did not show a decline of phytoplankton biomass under warmer conditions (Sebastian et al 2012;Winder et al 2012). However, both freshwater and marine mesocosm experiments agreed in demonstrating a dominant role of light for the determination of bloom biomass (Klauschies et al 2012).…”

“…The fundamental importance of light for the timing of phytoplankton blooms has also been shown by the Baltic Sea mesocosm experiments ) and the limnetic mesocosm experiments in Brunnsee (Berger et al 2007(Berger et al , 2010. Both increasing light and warming were shown to advance the phytoplankton spring bloom (Klauschies et al 2012;Winder et al 2012). While surface irradiance and turbidity dominate the effective light climate for phytoplankton growth in shallow water bodies, this role is taken by turbulent mixing and the seasonal shift between thermal winter mixing and summer stratification in deep systems (Peeters et al 2007a, b).…”

“…While a general trend toward earlier timing of seasonal blooms at warmer temperature was observed in marine and freshwater mesocosm experimental studies (Tirok and Gaedke 2007a, b;Winder et al 2012), this pattern is not consistent across ecosystems. For example, retardation by warming (Wiltshire and Manly 2004) or the absence of a response (Wiltshire et al 2008) was reported for the Helgoland time series, German Bight, North Sea.…”

“…The lake mesocosm experiments (Berger et al 2010;Sebastian et al 2012;Winder et al 2012) did not report cases of mismatch. In contrast, increased (light-dependent) algal production and increased (temperature-dependent) Daphnia growth both speeded up successional dynamics as shown in coupled Daphnia-phytoplankton models (Diehl 2007).…”

“…The diversity of methods, focal ecosystems, subsystems and organisms, and research questions precludes a statistical meta-analysis across ecosystems, although results were combined and contrasted to identify general patterns if possible (e.g., Winder et al 2012). Here, we highlight a selection of the most important findings from studies of this special issue and from AQUASHIFT articles published elsewhere.…”